The treatment of synthetic fibers to impart to them stain-release properties is well known in the art. The most common synthetics used as fibers are polyethylene terephthalate, polyamides, polyacrylonitriles, and polyolefins which possess a hydrophobic character, making their laundering (particularly as regards the removal of oily soil and oily stains) difficult. This is due in large part to the inherent low wettability of these synthetic fibers. Oily soil or stain is difficult to remove in an aqueous laundering process since the oily material tends to become attached to the hydrophobic, or oleophilic, fibers. Assignee's copending patent application, Ser. No. 146,149, filed May 2, 1980, in the names of W. K. Larson, M. M. Lynn, and E. S. McAlister discloses use of sulfonated polyester polymers to surface-modify shaped essentially polyester articles to provide them with a stain-releasing finish durable to multiple launderings, and this patent application is incorporated herein by reference. By "sulfonated" or "sulfo" is meant a --SO.sub.3 X group in which X is hydrogen or alkali metal cation, such as sodium, potassium, and lithium; alkaline earth metal cation; tertiary, and quaternary ammonium cations having zero to 18 carbon atoms, such as ammonium, hydrazonium, N-methyl pyridinium, guanidinium, methylammonium, butylammonium, diethylammonium, triethylammonium, tetraethylammonium, and benzyltrimethylammonium; monovalent cations are preferred.
It is known in the art to use water-soluble salts to help catalyze the cross-linking of permanent press resins for synthetic/cotton shaped articles. The use of water-soluble salts is well known in the dye industry to improve the exhaustion of certain dyestuffs. It is novel in the art, however, to use such salts in combination with soil-release agents in aqueous environments to improve soil-release properties. In general, such salts increase the durability of the treated synthetic fabric to laundering and at the same time reduce the concentration of surface-modifying agent used in the aqueous environment.